Remote host said: 550 No such user - psmtp [RCPT_TO]


We have two new users I set them up in AD  like anybody else. They have no problem to send/receive inbound email as well as send outbound email. But they are having problem to receive outboud email! I sent a few email  from my yahoo email account and got : Sorry, we were unable to deliver your message to the following address.

Remote host said: 550 No such user - psmtp [RCPT_TO]

Received: from [] by with NNFMP; 05 Oct 2011 15:40:15 -0000
Received: from [] by with NNFMP; 05 Oct 2011 15:40:15 -0000
Received: from [] by with NNFMP; 05 Oct 2011 15:40:15 -0000
X-Yahoo-Newman-Property: ymail-3
Received: (qmail 3634 invoked by uid 60001); 5 Oct 2011 15:40:15 -0000
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=s1024; t=1317829215; bh=7IKDjumCGXw6a8Bp5eyJbVBvgJQIg8vgh93TlElJMTg=; h=X-YMail-OSG:Received:X-Mailer:Message-ID:Date:From:Subject:To:MIME-Version:Content-Type; b=B1AxaEDdba5lnynb9ZXfAgc4DJHYI0TOY3SpQKE6txdDCbvG0VAhkEEpnRI4QEYkKU4TwpCP5chWP5obPTTvDrKiAXiqJOFVXgU+Tk0qHcEopkztIBihI/2tzWzgv100hon6vFZDKswMA5FMnrGaWvSzFCFqm8yR3H4XutYL+Cw=
DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws;

The error message is longer than above and I just copied some. By the way other users can be able to receive outboud email. We are using exchang2003 and Outlook 2007.

Can someone help me please?

Thank you very much in advance!
Who is Participating?
Alan HardistyCo-OwnerCommented:
Set the users up in your external Spam Filtering service (Postini) - you seem to be using a 3rd party to filter your mail and you haven't added their email addresses to their servers.
Hypercat (Deb)Commented:
As alanhardisty said - you left out the most important part of the header (the first part) which probably shows your internal email server receiving the mail from ""  This is the Google Postini domain that is obviously set up to pre-filter your incoming email for spam before it gets to your servers.  This service requires that you set up each new user on the Google Postini website for your firm as well as setting them up internally in Active Directory.  If you don't know how to do this, is there someone else you can check with who might have been the original person to set up this configuration for your company?
lgallionAuthor Commented:
I will look into it! Thank you so much!!
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